The invention relates to an electromotive linear drive, comprising a housing in which a drive unit is arranged, the output member of which is designed as a linearly movable spindle nut that is operatively connected to a connecting part for connection to a further component. The further component is preferably adjustable. The spindle nut can be rigidly connected to a lifting tube whose free end is coupled with the further component.
The electromotive linear drive in its preferred embodiment is a furniture drive for adjusting furniture components. Furthermore, the linear drive is a single drive in a preferred embodiment, i.e. a drive unit is arranged in the housing in order to adjust the lifting tube in the longitudinal direction which is to be coupled with a furniture component connected thereto.
All pieces of furniture in the domestic field and in the health care and hospital fields can be considered as pieces of furniture which are arranged for example as berths, beds, slatted frames, treatment couches, hospital nursing beds or, in the wider sense, patient lifts.
The drive unit consists of an electric motor that can be operated with a DC safety voltage, to which a speed-reduction gear such as a worm gear is connected. A spindle is driven by the speed-reduction gear, on which the spindle nut is placed which forms the output member. The spindle nut will move in operation in the direction towards the free end or in the direction towards the speed-reduction gear depending on the direction of rotation of the drive motor. The drive unit consists in this embodiment of the aforementioned components, but the lifting tube is a connecting part between the output member of the drive unit and the furniture components to be adjusted.
Electromotive linear drives of furniture drives are known in which the connected furniture component is adjusted electromotively in the normal operating state, i.e. when the furniture component to be adjusted is displaced by rotation of the spindle and by displacing the spindle nut, in which the spindle nut is held in a torque-proof manner by a fork head as the connecting part, wherein the fork head is placed on the end region of the lifting tube. Said fork head can be provided with a disconnecting clutch, so that spindle nut will rotate and will also still simultaneously be displaced in the longitudinal direction of the spindle when said disconnecting clutch is actuated.
If the speed-reduction gear is a worm drive, the axes of the drive motor and the spindle are disposed at a right angle with respect to each other. The flanged tube can be rigidly connected to the housing, i.e. it can be an integral formed part, but it can also be fixed to the housing by means of suitable fastening means. The lifting tube is guided in the flanged tube. The housing is usually made of two housing parts.
The components are made of plastic in the standard designs of the electromotive linear drive, with the exception the spindle, the worm and the drive motor which consists of steel.
Further components such as a switch can be installed in the flanged tube. The lifting tube usually has an annular cross-section.
The use of a disconnecting clutch is problematic for many purposes because the furniture component to be adjusted will be lowered suddenly during the disconnection of the clutch because the thread of the threaded spindle is not provided with a self-inhibiting thread. In order to prevent this is it is known to use a braking device that is complex in its configuration.
Furthermore, constructions with an interlocking coupling are known, wherein the actuation and handling thereof is very complicated and not user-friendly.